In certain applications, hydraulic fluid flow in hydraulic machinery may be controlled using hydraulic sectional control valves. A sectional control valve or valve assembly may include a plurality of separate cast and machined metal valve worksections. Each worksection may include internal fluid passages, external ports, and valve bores with valve members slidably disposed within each valve bore. The valve bores may include a main control valve spool bore in which a main directional control valve spool is slidably disposed, and a pressure compensator valve spool bore in which a pressure compensator valve spool is slidably disposed.
In a pressure compensated worksection, the pressure compensator valve spool is arranged to maintain a predetermined pressure drop across a variable orifice of the main control valve spool under normal operating flow conditions independently of the inlet or outlet pressure. By maintaining a substantially constant pressure drop across the variable orifice, a substantially constant flow rate through the variable orifice may be achieved for a given axial position of the main control valve spool.
Pressure compensated worksections may also commonly include load-sense passages. The load-sense passages may be operably connected to provide or transmit a pressure feedback signal from an outlet passage or workport. The pressure feedback signal may be referred to as a load-sense pressure signal and indicates the fluid pressure required by a fluid operated device, such as an actuator, which receives flow from the sectional control valve.
The load-sense passage may further be operably communicated to a load-sensing variable displacement hydraulic pump or other load-sensing source of pressure and flow. The load-sensing source is configured to provide enough flow at the load-sense pressure plus a margin pressure value. This flow is communicated via plumbing to the sectional control valve, where each actuated control section may consume a portion of the flow to drive an associated actuator.
In examples, if the several control sections are actuated at the same time, e.g., the spools in these control sections are moved at the same time, the demanded flow may exceed the flow that the load-sensing source is capable of supplying while maintaining the pressure margin value. As such, the flow reaching the sectional control valve might not have sufficient pressure to properly control the actuators. Further, in some examples, flow demand may suddenly decrease if, for instance, one or more of the actuated spools are returned to their neutral position. If the load-sensing source does not react sufficiently quickly to reduce its flow output, a flow surge may occur. The flow surge may cause undesired motion of the actuators.
It may thus be desirable to have a hydraulic control valve that improves regulation of the pressure and flow of fluid reaching a load-sensing valve from a load-sensing source.